This invention pertains to the field of exercise equipment, broadly to stationary walk, run, stepper, striding, and pedaling machines such as treadmills, cross-country skiers, steppers, and various pedal cycles and, more specifically, to walk-run pedal or foot pad type exercisers.
It has long been recognized that exercise involving the legs is best for accomplishing aerobic exercise necessary for total conditioning and cardiovascular health. But, in recent years it has also been found that the step-down impact produced in walking, jogging and running, including treadmill use, can cause debilitating damage to foot, ankle, knee and hip joints.
Some treadmills have been introduced to address this problem by adding cushioning means under the belt or the belt support deck. But, belt cushioning increases drag and belt wear and deck cushioning is relatively limited, since the movable mass is still substantial and the vertical deflection capability is small. Some treadmills provide cushioning on top of or under the belt, but this is very costly and/or belt durability is reduced. Also, treadmills, with the momentum of the moving belt, pulleys, and drive train, can be dangerous to less adept and older users since the belt continues to move if the user trips and falls or needs to stop quickly for any reason. Also, due mainly to belt drag, power consumption is high, making it difficult to design a practical user-powered treadmill or a durable, yet low cost powered one.
Steppers and climbers generally produce more vertical foot motion than horizontal, simulating stepping up-down or climbing stairs, most having some incidental horizontal motion component due to pivotal action of the pedals on levers or an inclined guide track. These typically allow variable stroke steps and stopping within a single step, but the predominant motion is up and down and they are harder on ankle, knee and hip joints due to high joint articulation angles compared to normal, primarily horizontal walk-run strides. Also, these machines do not involve as much the large hamstring leg muscles as do the long, predominantly fore and aft strides of walking and running, and are not conducive to good cardiovascular workouts with minimum strain.
Pedal cycles, though involving the hamstring muscles more than steppers and climbers and allowing relatively quick, safe stops, especially the sitdown types, still require high hip and knee joint articulation and strain. They do avoid the impact inherent in treadmills, somewhat offsetting the high articulation strain. However, a largely unspoken disadvantage of pedal cycles, a result of pedal stroke being controlled by a rotating crank, is the constant stroke. This prevents any change in stroke or stride as can and does occur without any lost motion in normal walking, jogging and running. Thus, pedal cycles are constraining and become laborious or tedious sooner than treadmills and are more likely to be underused or worse, unused, a major problem in exercise equipment.
A recent variation of the pedal cycle elongates the pedals horizontal stroke while reducing vertical displacement so the resulting elliptical foot motion is closer to that of walking or running and at low impact. But, the laborious-tedious factor due to the constant, crank-controlled stroke is still present. Also, the fixed stroke as supplied may not be suitable for many people, since there is a wide range of sizes, strides, ages and abilities to satisfy.
Another exerciser, the cross-country skier, involves the hamstring muscles and minimizes impact and joint articulation, the feet moving attached skis backward against a resistance and being free to return at any length of stride. But, the attached skis' mass and length, and a need to pull the ski forward with the foot at the end of each stroke results in, again, a more constrained and laborious feel compared to normal walk-run action.
Various simpler exercisers, typically called striders, involve pedals or foot pads that move back and forth, staying in a single plane or arc. Another provides vertical motion independently of its back and forth motion, but balances the user's weight between the two pedals. These all allow variable length strokes or strides, but none provides the easy, normal walk-jog-run action of stepping down on, and transferring essentially all the weight to the forward foot, and freely swinging the unweighted trailing foot forward while pushing back on the weighted foot, then stepping down to end the stride at any point in each stride, from one stride to the next. These “strider” devices allow only balancing the user's weight more or less continuously between the two pedals while the feet are pushed backward and forward in equal strokes in opposite directions from the user's center of gravity. Again, this results in a constrained and laborious feel, unlike normal walk-run action in which each leg is unweighted on each forward return stroke.
Of the entire field of stand-up leg working exercisers, only the treadmill provides a realistic, normal walk-run experience as described, and its continuing popularity in the face of many and varied pedal and foot pad type machines being introduced, indicates that this normal walk-run action is an important desired characteristic. The primary detracting characteristics, high impact, inability to stop quickly, and high belt drag and power requirement are difficult to improve upon within the context of the continuous belt treadmill design at reasonable cost. An additional drawback of the typical motor driven belt treadmill is that any change in stride length must be accompanied by an instant related change in strides per unit time unless the belt speed is adjusted. On user powered, flywheel speed regulation treadmills, one can change stride, although not quickly, without a corresponding rate change, since foot force and motion powers the belt. But, the high belt drag and the attendant high angle of incline typically required for the user's weight to be employed to move the belt is a big negative.
Among the wide variety of pedal or foot pad machines, only the elliptical motion cycle seems to provide a reasonable approximation of the normal walk-run action, but stroke or stride is not automatically variable, though some may be adjustable. Of all the pedal or foot pad type machines allowing variable strokes or strides, none provides realistic, normal walk-run stride action including forward foot step down with essentially full weight transfer to that foot (involving placement of the user's center of gravity essentially directly above it), and a largely unweighted opposite, returning foot, free of any parts of the machine with automatically varying stride lengths from stride to stride.
Comparing walking in-place on a machine with walking on the ground or floor, it should be noted, there are some subtle differences. In ground walking, at forward foot step-down, marking the end of a stride, the body center of gravity is initially positioned slightly behind the step-down point, the body moving forward and rocking forward over the step-down point as the weighted foot starts to push rearward in the next stride. In-place walking, with no forward body momentum, involves stepping down essentially always at the same point directly under the center of gravity unless the user is holding on to handrails or the like and pushing the belt rearward or resisting its motion. Longer in-place strides, then, involve pushing back farther from a more or less fixed step-down point, and strides are shortened by simply stepping down sooner with the returning foot. It can be seen that machines having pedals or foot pads simply connected for equal and opposite back and forth motion can not be used for varying length realistic walking or running strides. If a user starts with both pedals abreast and pushes back with the weighted foot, the opposite pedal moves forward an equal distance, far ahead of his center of gravity. Then, if the user shifts his body position to be over the far forward position at step-down after a long stride, and makes only a short stride on the next push back, the opposite returning pedal will come back only a short distance from the previous long stride, far short of the user's center of gravity. Any change of stride will result in a change in return distance of the returning pedal, not to the required constant step-down position. Thus, machines directly connecting the pedals for equal and opposite back and forth motion do not provide realistic, normal walk-run action with variable length strides. They allow only moving the feet back and forth about the body's center of gravity, always essentially equally weighted or, in some cases, allow only fixed stride lengths with normal walk-run action. Striders having no pedal return means require the user to keep his feet always essentially equally weighted and no step action as in normal walking is possible.
Therefore, existing foot pad or pedal exercisers do not provide realistic, normal variable stride length walk-run action as on a treadmill, and treadmills do not provide the low impact at step-down or quick stop capability of some foot pad or pedal machines. Also, the typical motorized treadmill does not allow freely varying stride length without immediate compensating varying of stride rate or manually adjusting the belt speed. Additionally, no existing exerciser allows stride for stride changing between walking, jogging, running, and stepping action.